1. Field of the Invention
This invention is related in general to the field of emergency lighting and, in particular, to remote control and monitoring of emergency lights.
2. Description of the Related Art
Emergency lighting is required by most safety codes in the United States. Emergency lights provide temporary lighting in the event of a power failure. During normal operation, power is provided from power mains to operate the lamp and to charge a backup power source (e.g., a battery). When power from the mains is interrupted, the backup power source provides power to the lamp for a limited time (typically 90 minutes).
It is desirable to test emergency lights periodically to ensure proper operation. A typical prior art self test is initiated by a person pushing a button or flipping a switch on the lighting unit. Simple voltage and/or current tests are performed and a light or buzzer is activated if a test fails.
There are several problems with the prior art. One problem is that safety codes typically require a brief (i.e., 30 seconds) test be performed every month and a longer (i.e., 90 minutes) test be performed each year. The prior art requires a person to manually initiate, monitor, and record each of these tests. This is a large problem in a building which has many emergency lighting units. Consequently, testing is easily neglected, records of the tests are easily lost, and costs for personnel to perform the testing and recording of the test results are incurred.
Many systems and methods have been devised to perform emergency lamp testing. One such system is disclosed in U.S. Pat. No. 5,666,029, issued Sep. 9, 1997 to McDonnell and is incorporated herein by reference. McDonnell describes a self test circuit and method for testing the emergency ballast for a flourescent lamp. It describes circuits for measuring backup power source voltage and current to the lamp. McDonnell, however, does not provide a solution to the several problems mentioned above. A person must still manually initiate the self test, monitor the test, and record the test results.
Another reference is disclosed in U.S. Pat. No. 5,148,158, issued Sep. 15, 1992 to Shah. Shah describes an emergency lighting unit with remote test capability. The lighting unit taught by Shah can initiate a self test via a hand-held remote control. Shah""s invention eliminates the need for a person to press a test button mounted on the emergency lighting unit. An operator uses a remote controller to initiate tests from a distance of several yards from the lighting unit. However, Shah fails to provide a solution to several problems. Using Shah""s invention, a person must still manually initiate the self test, monitor the test, and manually record the results of the tests.
Another problem with the prior art is that repairs and adjustments are done manually. This is expensive and time consuming. These tasks require that a person manually test the lighting unit, verify that a problem exists, diagnose the problem, and fix the problem.
Clearly there exists the need for an improved emergency lighting test system which automatically initiates emergency lighting tests, monitors the results of the tests, automatically records test results, performs these functions from one central location, monitors lamp light output, adjusts lamp light output, diagnoses failures, predicts failures, is a simple design, and is cost effective.
The invention discloses an emergency lighting monitoring and control system which remotely controls, monitors, and tests the emergency lights in a building. A central control unit schedules tests for each of the emergency lights, remotely initiates the tests, monitors the test results, stores test reports, and notifies an operator of failures. The self tests include backup power source tests and lamp tests. Some problems are automatically fixed by the system. The system predicts failures and suggests which component to replace when a test fails. An operator can program new test schedules, turn the emergency lights on and off, and view the test reports. The system is expandable and automatically detects newly installed emergency lighting units.
The central control unit communicates with all of the emergency lights in the building using wireless technology. The invention significantly reduces costs and increases reliability of the testing process by eliminating the need for a person to physically go to each emergency light, initiate tests, and record the results of the tests.
The central control unit is located in a convenient location. A flat panel, touch screen provides the user interface for the system. The flat panel is designed to be recess or surface mounted on a wall or console. Using the simple touch screen interface, the operator views test reports, schedules tests, initiates tests, and sends commands to the emergency lighting units.
Both the central control unit and the emergency lighting units include radio transceivers which permit communications between the units. For very large buildings or where radio interference is a problem, the invention uses a repeater. The repeater is positioned in a location where it can receive and transmit radio signals between the control unit and the emergency lighting units. Radio frequency communications also saves the time and expense of installing wire communications lines.
When the system is initially installed, the control unit automatically learns the ID numbers of all the emergency lighting units in the building. The control unit broadcasts a command to all lighting units causing them to transmit a reply. The control unit stores the ID numbers of all the replies received. This feature simplifies installation and is also useful when installing additional lighting units.
The central control unit contains a testing schedule which is stored in memory. The schedule preferably conforms to local or national safety codes. When a test is scheduled, the control unit sends a command to the specific lighting unit to initiate the test. The command specifies the type and duration of test to be performed. During long duration tests (e.g., 90 minutes) the control unit periodically sends commands to the lighting unit to verify the test is proceeding.
When the test is complete, the lighting unit transmits a data packet to the central control unit. The data packet contains status data about the tests performed and the results of the tests. The control unit analyses the status data from the lighting unit and stores a report of the test in memory.
In addition to initiating tests and generating test reports, the control unit analyzes the status data for other purposes. The control unit determines the cause of a failure and also predicts future failures. Determining the cause of a failure facilitates a quick and cost effective repair. A failure is predicted, for example, by monitoring a parameter. If the parameter drifts closer to a fail limit value over a period of time, then the controller will notify the operator of a predicted failure. This test is easily implemented by storing a history of test results. The control unit analysis the test results to predict the failure.
The invention also monitors status data from the emergency lighting units to verify nominal light output of the lamp. Light output can be estimated by measuring an appropriate parameter (e.g., battery discharge current). If the current is less than a predetermined value, the inverter is put into a higher current output mode causing the lamp to output more light. Conversely, if the discharge current is too high, the inverter is put into a lower current output mode causing the lamp to output less light.
Therefore, an object of the invention is to provide an improved system and method for remotely testing and monitoring emergency lighting units.
A feature of the invention is a central control unit which is in communication with a plurality of remote emergency lighting units.
Another feature of the invention is a central control unit which initiates self tests of the emergency lighting units.
Another feature of the invention is a central controller which communicates with emergency lighting units via electromagnetic signals.
Another feature of the invention is a central control unit which generates and stores reports of test results.
Another feature of the invention is a central controller which automatically detects the emergency lighting units in a building.
Another feature of the invention is a repeater which relays messages between a central control unit and an emergency lighting unit.
Advantages of the invention include reduced operating costs, reliable scheduling of tests, reliable recording of test results, quick diagnosis of failures, advance prediction of failures, reduced installation costs, and automatic compliance with safety codes for periodic testing.
Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose only one of the various ways in which the invention may be practiced.